Flotation process



Patented Oct. 29, 1946 FLO'IATION PROCESS Fred D. De Vaney, Hibbing,Minn, assignor to Erie Mining Company, Hibbing, Minn., a corporation ofMlnnesot No Drawing. Application April 26, 1944, Serial No. 532,867

Claims.

This invention relates to specific improvements in the froth flotativebeneficiation of silicious iron ores, and is specifically concerned witha mode of accelerating the rate of flotative separation of siliciousgangue from such ores using higher molecular weight aliphatic aminecompounds as cationic collectors.

It heretofore has been suggested that silicious iron ores might bebeneficiated by froth-floating the silicious gangue particles from theiron mineral particles of a pulp of the ore by the use of a highermolecular weight aliphatic amine compound, having from 10 to 18 carbonatoms in the aliphatic radical, as collector in conjunction with asuitable frother. According to the suggested technique the pulp circuitwas to be maintained distinctly alkaline; preferably, also, theflotation was to be effected in the presence of a selectivityimprovingagent such as acid-treated starch.

the ore pulp a relatively small amount of an alkali metal sulfide(specifically, sodium sulfide), the rate of flotation of the siliciousgangue particles can be very materially increased, with no decrease inthe selectivity and with a small but appreciable saving in the amount ofamine collector required. As equivalent of sodium sulfide there may beused potassium sulfide or calcium sulfide or barium sulfide or apolysulfide of sodium, potassium, calcium or barium.

It has been found that the alkali ,metal or alkaline earth metal sulfideor polysulfide functions most effectively when the pulp circuit ismaintained acid (i. e., less than pH 7) rather than alkaline.

The influence of progressive additions of sodium sulfide, whilemaintaining a constant pH, may be seen from the data of the followingtable:

TABLE 1 Effect of sodium sulfide on amine flotation oi Mesabi washingplant tailings t r nt. Assay}, P t so um percen ercen sulfide, Producttotal g g lbs/ton iron n Iron Silica Silicious froth. 82. 41 8. 95 41.01 Concentrate.--.- 17. 59 60. 24 8.15 58. 99 min 25 sec.

Total. 100.00 17. 97 100. 00 Silicious froth. 82. 86 8 85 41. 36 o 2Concentrate... 17. i4 60. 61 8.02 58. 64 min Total... 100.00 17. 72 100.00 Silicious froth. 82. 48 8. 63 39. 92 Concentrate".-. 17.52 61. 217.17 60.08 3 min" 25 sec Total. 100.00 i7. 84 100.00 Silicious froth.-.83. 06 9. 61 44. 42 m8 Concentrate..- 10. 34 61. 54 6. 55. 58 3 min,

Total. 100. 00 18. 10 100. 00 Silicious froth. 84. 50 9. 98 47. 54Concentrate... 15. 50 59. 75 9 34 52. 46 2 mm" 35 Total. 100. 00 17. mo.00

Norm-In each test 500 gm. of washing plant tailing were treated withoutadditional crushing and without desliming in a 500 gram Denver Sub Aflotation cell. The pulp in each case was maintained at an acidity of pH5.2. The flotation reagents used in each test were Identical andconsisted of 0.4 lbJton of AM Coco," i. e., a canonically-actingcollector consisting of the hydrochlorides. acetates or otherwatersoluble forms of mixed primary aliphatic amines corres nding inaliphatic chain length to fatty acids of coconut oil, made by Armour &ompan and .104 lb./ton of methyl amyl alcohol which were added in smallincrements. hen sodium sulfide was used this reagent was conditionedwith the pulp for 5 minutes prior to flotation.

It has now been found that if with the usual higher molecular weightaliphatic amine collector aforesaid and suitable frother there be addedto The infiuence of varying the acidity of the pulp circuit, whilemaintaining constant the amount of sodium sulfide (and all othervariables) at arbitrary levels, may be seen from the data of thefollowing table:

' TABLE 2 increased rate of flotation means that a flotation Efl'ect ofvarying pH of pulp on amine flotation of Mesabi washing plant tailinasAssay percent pH of PM at Percent f'ggf Total flotation pulp wt. timeIron Silica Siliclcus froth 80. 90 7. 99 B6. 64 a o Concentrate... 19.10 58. 72 9. 79 63. 46 3 mm. a) m.

Total. 100.00 17.68 100.00 silicious froth. 79. 8. 00 35. 39 v 7.1Concentrate- 20. 34 5?. 16 12. 63 64. 61 5 mm.

Total. 100. 00 18. 00 100. 00 silicious froth- 7a 73 7. 61 33. 28 aConcentrate"-.. 21. 27 65. 69 14. 61 06. 72 5 mm" 45 m.

I Total- 100. 00 17. 76 100. 00

Test conditions same as given in Table 1, except 0.5# fused sodiumsulfide used in all tests and alkalinity and acidity controlled byaddition of either sulphuric acid or sodium carbonate.

By using in the pulp circuit both the sulfide and the acid-treatedstarch it is possible to maintain the high selectivity attributable tothe use of the starch material while simultaneously achieving the highrate of feed made possible by use of the sulfide.

EXAMPLE The starting material was a washing plant tailing from theDanube mine, Minnesota, analyzing 16.66% Fe, mostly as hematite. Thesilicious gangue was mostly quartz. The material as obtained wasessentially of a size through 48 mesh and was not further subdivided.

The starting material, without having been subjected to a deslimingtreatment, and in the form of an aqueous pulp of approximately solids,was added to a mechanically agitated flotation cell, and to it wereadded 0.5 lb./ton of acid-treated starch, /4 lb./ton of sulfuric acidmonohydrate, and 0.8 lb.-/ton of sodiumlsulflde in the form of 60% fusedflake. Afterthorough mixing of these ingredients with the pulp andconditioning for 3 minutes, froth flotation was induced by the additionof 0.25 lb./ton of 9AM (.looo collector and 0.05 lb./ton of B-23"frother, both of which agents were added, in small inmany flotationcells to handle the same tonnage alkali metal or alkaline earth metalsulfide or crements, during the agitation and aeration of Per cent Percent Per cent Per cent Pmdm wt. Fe SlOl total iron silicious froth(tailing)--- 60. 24 5. 71 20. 2d lrotli (middling) 23. 62 13. 86 10. 63Concentrate l6. 14 61. 66 7. 45 59. 72

It is to be noted that the time required for the over-all flotation(both roughing and cleaning) was 3 minutes and 15 seconds, whereas inthe absence of the sodium sulfide the normal flotation time is from 5 to6 minutes. This greatly polysulfide is used appears to be due to aselective fiocculating effect of the sulfide or polysulfide on thegangue particles. Whatever may be the correct explanation, it is anobservable fact that, with use of the sulfide or polysulfide,flocculation of the gangue particles does take place, and thisflocculation of the ga'ngue is definitely a very desirable condition forrapid flotation.

I have found that non-alkali inorganic sulfides such as ammonium sulfideand hydrogen sulfide not only do not serve to accelerate the rate ofseparating but positively are harmful in the flotation. A number ofexperiments with organic I compounds of sulfur, e. g., petroleumsulfonates,

sulfonic acids and a number of xanthates, have established that suchcompounds are not helpful for accelerating the rate of flotation.

It is tobe noted, in this connection, that the function of the alkalimetal or alkaline earth metal sulfide or polysulfide is not that of asulfidizing agent toward the mineral to befloated,

as obtains in the flotation of base metal ores,-e. g.,

oxidized copper and lead ores. where a sulfide actually forms a basemetal sulfide "sheath or surface layer on the mineral particle. In thepresent process, no chemical combination between the silica and thesulfide or polysulfide of sodium, potassium, calcium or barium has beenobserved.

I claim: a

1. In the process of beneflciating silicious iron ore by cationicallyfroth-floating the silicious gangue particles from the iron mineralparticles of an aqueous pulp of such an ore by the use of a highermolecular weight aliphatic amine collector and a frother, the step ofaccelerating the rate of flotation of the silicious gangue particleswhich consists in incorporating a relatively very small amount of sodium.sulfide into the pulp prior to the froth flotation step.

2. In the process of benefic'iating silicious iron ore by cationicallyfroth-floating the silicious gangue particles from the iron mineralparticles of an aqueous pulp of such an ore by the use of a highermolecular weight aliphatic amine collector and a frother, the step ofaccelerating the rate of flotation of the silicious gangue particlesimproving agent, steps of accelerating the rate of flotation of thesilicious gangue particles which consists in maintaining the pulpcontaining the aforesaid agents at a pH of less than 7 but not less thanabout 5 and incorporating into the acidic pulp, prior to the frothflotation step, a relatively very small amount of sodium sulfide.

4. In the process of beneficiating silicious iron are by cationicallyfroth-floating the silicious gangue particles from the iron mineralparticles of an aqueous pulp of such an ore by the use of a highermolecular weight aliphatic amine collector and a frother, the step ofaccelerating the rate of flotation of the silicious gangue particleswhich consists in incorporating a relatively very small amount of analkali metal sulfide into the pulp prior to the froth flotation step.

5. In the process of beneficiating silicious iron ore by cationicallyfroth-floating the silicious gangue Particles from the iron mineralparticles of an aqueous pulp of such an ore by the use of a highermolecular weight aliphatic amine collector and a i'rother, the step ofaccelerating the rate of flotation of the silicious gangue particleswhich consists in incorporating a relatively very small amount of analkali metal polysulfide into the pulp prior to the froth flotationstep.

6'. In the process of beneficiating silicious iron ore by cationically:froth-floating the silicious '1. In the process of beneflciatingsilicious iron ore by cationically froth-floating the silicious gangueparticles from the iron mineral particles of an aqueous pulp of such anore by the use of a higher molecular weight aliphatic amine collectorand 01' a frother, in a slightly acidic circuit, the step of selectivelyfiocculating the silicious -gangue particles which consists inincorporating into the pulp, prior to the flotation operation, arelatively small amount of a compound of the group consisting of thealkali metal sulfides, the alkaline earth metal sulfides, the alkalimetal polysulfides and the alkaline earth metal polysulfldes.

8. The process of beneficiating a silicious oxidic iron ore, whichcomprises adding to an aqueous pulp of the ore a mineral acid in anamount sufllcient to give the pulp a pH of about 6.0, conditioning thepulp with from about 0.4 lb. to about 1.6 lbs/ton of a compound of thegroup consisting of alkali metal sulfides, alkaline earth metalsulfides, alkali metal polysulfldes and alkaline earth metalpolysulfldes, and subjecting the acidified and conditioned pulp to frothflotation in the presence of a frother and of a higher molecular weightaliphatic amine collector, thereby rapidly raising a froth product richin silicious gangue particles.

9. The process of beneflciating a silicious oxidic iron ore, whichcomprises adding to an aqueous pulp of the ore a mineral acid in anamount sufllcient to give the pulp a pH of about 6.0, conditioning thepulp with acid-treated starch and from about 0.4 lb. to about 1.6lbs/ton of a compound of the group consisting of alkali metal sulfides,alkaline earth metal sulfides, alkali metal polysulfides and alkalineearth metal polysulfldes, and subjecting the acidified and conditionedpulp to froth flotation in the presence of a frother and of a highermolecular weight aliphatic amine collector, thereby rapidly raising afroth product rich in silicious gangue particles while depressing fineoxidic iron particles into the underflow product.

gangue particles "from the iron mineral particles of an aqueous pulp ofsuch an ore by the'use of a higher molecular weight aliphatic aminecol-:'

lector and 'a-frother, the stepof'accelerat'ing the rate of flotation ofthelsilicious gangue particles which consists in incorporating arelatively very small amount of a compound of the group conslsting ofthe alkali metal sulfides, the alkaline earth metal sulfides, the alkalimetal polysulfldes and the alkaline earth metal-polysulfides into theoulp prior to the froth flotation.

10. The process of 'beneflciating a silicious oxidic iron ore, whichcomprises adding to an aqueous pulp of the ore a mineral acid inanamount sufficient to give the pulp a pH of about 16.0, conditioningthe pulp with from about 0.4 lb.

to about '1.6 lbs/ton of sodium sulfide, and subjecting the acidifiedand conditioned pulp to froth flotation in the presence of a frother andof a primary alkylamine having from 10 to 18 carbon atoms in the alkylradical as collector, thereby rapidly raising a froth product rich insilicious gangue particles.

FRED D. DE VANEY.

